Power hacksaw



G. J. BLUM POWER HAcKsAw sept. 4, 1934.

Filed June 22. 1931 3 Sheets-Sheet l Sept. 4, 1934. G. J. BLUM 1,972,328

POWER HACKSAW Filed Jpme 22. 1931 5 Sheets-Sheet 2 Y O 101 23 95 l 10095 95 97 2 109 Q 98 l; l 05 I f G. J. BLUM POWER HAcxsAw Sept. 4, 1934.

Filed June 22. 1931 5 Sheets-Sheet 5 lill ll'llllllllll lOl PatentedSept. 4, 1934 UNITED STATES PATENT OFFICE strong-Blum Mfg. Co., Chicago,Ill., a corporation of Illinois Application June 22, 1931, Serial No.545.949 i 20 Claims.

The invention relates to power hacksaws for sawing bars of metal orother material into desired lengths, the machine being entirelyautomatic so that it is only necessary to place a bar of material in themachine, make the proper adjustments, and start the operation.

One of the principal objects of the present invention is to provide ameans for automatically throwing out the feeding mechanism, in

0 a machine of this character, should the downward feeding movement beobstructed at any point, so that none of the parts of the machine willbe broken.

A further object is to provide a new and irnproved construction by whichthe blade is raised from the stock. during the back stroke of the bladeand depressed during the cutting stroke, and which is coupled with themeans for throwing out the feeding mechanism.

Another object is to provide a construction by which the blade is raisedfrom the stock during the back stroke of the blade and depressed duringthe cutting stroke, and which is yieldable to avoid damage to themachine should any obstruction occur.

Another object is to provide means for positively throwing out thefeeding mechanism at the top of its stroke, should the reversingmechanism fail to act.

Still another object is to provide an improved construction of thefeeding mechanism.

Further objects reside in an improved construction of the device forstopping the machine automatically at the end of a single cut, in animproved counterbalance for the head, and in improvements in the meansfor drawing the stock forwardly for a new cut.

Other objects and advantages will become apparent from the followingdescription taken in connection 'with the accompanying drawings, inwhich:

Figure 1 is a perspective view of a machine embodying the features ofthe invention.

Fig. 2 is an enlarged fragmentary elevational view of the device forstopping the machine after a single cut.

Fig. 3 is a front elevation, partially in section, of the machine.

0 Fig. 4 is a fragmentary sectional view taken on the line 4-4 of Fig.3.

Fig. 5 is an elevation, partially in section, of a portion of thefeeding mechanism.

Fig. 6 is a fragmentary view taken substan- 55 tially on the line 6-6 ofFig. 5.

(c1. zii- 73) Fig. '1 is a sectional view taken substantially on theline 7-7 of Fig. 5.

Fig. 8 is a fragmentary sectional view taken substantially on the line8-8 of Fig. 5.

The machine in general this upright is a horizontally extending bracket22 providing a support for a horizontally reciprocable frame 23 carryinga saw blade 24. Vertical movement is imparted to the bracket 22, andthereby to the frame 23, through the medium of a feed screw 25 arrangedto be actuated in opposite directions by a pawl and ratchet echanismgenerally designated by the numer- Reciprocatory motion is imparted tothe saw frame 23 by means of a crank arm 30 (Fig. 3) oscillated in therotation of a shaft 31 and connected to the frame 23 by means of apitman 32. Also, actuation of the pawl and ratchet feed mechanism 26 iseffected from said shaft 31 by means of a lever 33 fulcrumed between itsends and connected at one end to the crank arm 30 by means of a link 34.The other end of the lever 33 has a pivotal connection with a rack bar35, the latter constituting the driver for the pawl and ratchetmechanism 26. Since this actuating mechanism is generally of the samecharacteras that shown in my said copending application, a detaileddescription thereof is deemed unnecessary.

Feeding mechanism The pawl and ratchet mechanism 26 for ac- 95 tuatingthe feed screw 25 includes, as in the case of the case of the machineshown in my copending application, a ratchet wheel 40 (see Figs. 5, '7and 8) secured to .the feed screw 25 and constituting, together with anactuating pawl 41, an actuator for effecting an upward movement of thebracket 22. The mechanism also includes a pair of ratchet wheels 42 and43, with driving pawls 44 and 45 therefor, for effecting a downwardfeeding movement of the feed screw 25. The ratchet wheel 43 is connectedto the ratchet wheel 40 for rotation therewith, thus being capable ofimparting a positive feeding movement to the feed screw, while theratchet wheel 42 is interposed between and has frictional contact withthe other two wheels to impart to the feed screw a non-positive movementof an extent depending upon the resistance offered to the downwardfeeding movement of the saw. The ratchet wheel 42 is capable of actingthroughout the entire cutting stroke of the saw, while the ratchet wheel43 is limited in its action only to the latter part of the cuttingstroke by means of an adjustable guard ring 46 (Fig. 8) surrounding theratchet wheel 43 and having a slot 47 cut therein. During the majorportion of the cutting stroke, the pawl slides on the periphery of theguard ring 46, but toward the end of the stroke, the pawl moves throughthe slot in the guard ring and into engagement with the ratchet wheel43.

The ratchet wheel 43, as in my copending application, is adjustableaxially of the feed screw 25 to vary the frictional engagement of theratchet wheel 42 with the other two wheels. Thus, a spring 50 is coiledabout the upper end of the feed screw 25 and bears between the ratchetWheel 43 and an adjustable nut 51 threaded on the feed screw.

The present invention provides means (Fig. 5) eliminating any tendencyof the nut 51 to rotate out of a set position, and yet permit it to bereadily adjusted when so desired. To this end, a washer 52 is interposedbetween the spring 50 and the nut 51 and is retained against rotationrelative to the feed screw as by a tongue 53 extending into alongitudinal groove 54 cut in the feed screw. The abutting end faces ofthe nut 51 and washer 52 are correspondingly serrated, as indicated at55, to prevent relative rotation when the spring 50 holds said facestogether. 'I'he serrations 55 are rounded off so that, when itis desiredto turn the nut 51, the nut and washer may be readily cammed apartsuiciently to permit the serrations to pass each other.

The driving pawls 41, 44 and 45, as in the machine shown in my priorapplication, are mounted in a shiftable carrier which is oscillated inthe reciprocation of the rack bar 35. This carrier is pivotally mountedon a crank arm 56 rigid with a gear segment 57 (Fig. 7) which mesheswith the rack bar 35. The pawl carrier is in the form of a U-shapedmember 60 (Fig. 5) having its ends mounted to turn on a pin 61 mountedvertically on the free end of the crank arm 56, the latter beingconstructed to provide a rigid frame member 62 (Fig. 6) in which theupper and lower ends of the pin 61 are mounted. The driving pawls 4l, 44and 45 are pivotally mounted on the pin 6l, and the carrier 60 isshiftable from a neutral position to one side of such neutral positionto place the pawl 41 in an operative position, or to the other side ofsuch neutral position to place the pawls 44 and 45 in operativepositions, the carrier being held in any of such positions by means of aspring detent 63.

The pawls 41 and 44, since they are used alternately, are formedintegrally on a block 64 which is normally held in a neutral position bya spring detent. According to the present invention, the spring detentis of a simplified construction, is inexpensive to manufacture, andefficiently holds the pawls in operative position when the carrier 60 isso shifted. To this end, a plate 65 (see Figs. 5, 6, 7 and 8) ispivotally mounted on the outer face of the carrier by means of aninwardly turned fiange 66 on the plate 65 resting on the upper edge ofthe carrier and held in such position by a coiled spring 67 bearing onthe outer face of the plate 65 and against an abutment on a pin 68extending from the carrier. The lower end of the plate 65 is punched toform two pins 69 extending at right angles to the plate and through apair of holes in the carrier 60 to bear against the block 64 on oppositesides of the pivot pin 61.

In the operation of the pawl and ratchet device, when either the pawl 41or the pawl 44 is thrown into an operative position by shifting thecarrier 60 from neutral to one side `or the other, either pawl, inpassing over the teeth of its ratchet, is cammed aside so that the block64 is turned on the pin 61. The pins 69 on the plate 65 are swungoutwardly against the action of the spring 67 until the pawl passes overthe ratchet tooth, when the pressure of the spring turns the block 64back to bring the pawl in an engaging position. Thus, each pawl acts onits ratchet in the usual manner but the construction is simplified bythe use of a single spring acting on both of the pawls.

The pawl carrier 60 may be automatically shifted from one operativeposition through neutrai and to the other operative position, to causethe feed mechanism to move the bracket up or down, as in the case of themachine shown in my copending application. The pawl carrier 60 may alsobe shifted to and locked in its neutral position by means of a slide 70having a projection 7l movable into engagement with a pair of spacedlugs 72 formed on the under side of the pawl carrier 60 on oppositesides of the pivot pin 61, the projection 71 turning the carrier aboutthe pin 61 until the projection 71 bears against both lugs 72.

Safety features of the feed mechanism One of the chief features of thepresent invention is a means for automatically throwing out the feedmechanism 26, should the downward feeding movement be obstructed at anypoint. in order to avoid breakage of any parts of the machine. This iscoupled with a new and improved means for raising the saw blade duringthe back stroke, the last-mentioned means being yieldable in characterand adapted to actuate the means for throwing out the feed mechanism onyielding.

The means for raising the saw blade from the work during the back strokeand depressing the blade during the cutting stroke operates, in thepresent embodiment (see Figs. 3 and 5) on the feed screw 25 which isthreaded in a nut 80 formed on the bracket 22. The feed screw is free tobe moved longitudinally up and down to an extent which is sufficient toraise the saw slightly out of cutting contact with the work. Suchlongitudinal movement of the feed screw is limited in a downwarddirection by a thrust bearing 81 positioned in a ledge 82 formed withinthe column 21, and in an upward direction by a collar 83 secured to thescrew and adapted to abut against a second ledge 84 formed within thecolumn 21 and spaced from the first ledge 82.

The means for raising the feed screw comprises a spring 85 bearingagainst the ledge 84 and against a collar 86 secured to the feed screw.Opposing the tendency of the spring 85 to raise the screw is a means fordepressing the screw comprising, in the present embodiment, a lever 90having a fork 91 at one end embracing the feed screw and bearingdownwardly on the collai` 86, a thrust bearing 92 being interposedtherebetween to prevent the screw from binding when depressed. The lever90 is mounted on a fixed pivot such as a pin 93 extending from a lug 94formed on the side of the column 21.

To swing the lever 90, a second or auxiliary lever 95 is pivotallysupported between its ends on the other end of lever as by a pin 96. Thesecond lever carries a roller 97 at one end which bears on theperipheral surface of a cam 98 carried on the main shaft 31.

The second lever 95 is adapted to be yieldably held in such positionrelative to the flrst lever 90 that the two levers move normally as aunit. To this end, an overhanging lug 100 is formed on the first leveradjacent the end of the second lever opposite to the end carrying theroller 97, and a rod 101 is adjustably secured in said lug and extendsthrough the adjacent end of the second lever. A compression spring 102is coiled around the rod 101 and bears against the second lever to holdit yieldably in abutment with the overhanging lug 100. Thus, on rotationof the main shaft 31, the cam 98 will raise the roller 97, and the twolevers swinging as a unit will depress the feed screw 25, while thespring 85 will raise the feed screw and swing the levers back when thehigh point of the cam has passed the roller. Since both the cam 98 andthe crank 30, through which the saw is reciprocated, are driven by themain -shaft 31, the relation between the cutting and back stroke of thesaw and the raising and depressing thereof may be properly timed.

In the operation of the hacksaw, if there should be an obstructionpreventing the depression of the saw by the lever 90, the second lever95, being pivoted on the first lever and being yieldably held inabutment with the lug 101, may turn relative to the first lever andcompress the spring 102. Thus, the cam 98 will move the second leveralone while the first lever remains stationary.

As mentioned above, when such an obstruction occurs as to cause thesecond lever 95 to yield relative to the first lever, meansautomatically throws out the feed mechanism. To this end, said means isprovided for connecting the second lever 95 with slide 70 of the feedingmechanism whereby the slide is moved to the position in which the pawlcarrier 60 is shifted and locked in its neutral position, when thesecond lever 95 yields relative to the first lever 90.

In the present embodiment, said connecting means comprises a rod 103extending through a fork 104 formed on the end of the second lever 95and yieldably secured so as to be moved thereby, by means of a pair ofsprings 105 coiled about the rod on opposite sides of the fork 104. Theupper end of the rod 103 is secured to one end of a bell crank 106pivoted on the column 21. The other end of the bell crank 106 extendsadjacent a lug 107 (Fig. 5) formed on the slide 70. A handle 108 is alsoformed on the end of the bell crank to which the rod 103 is attached topermit the crank to be operated manually.

In the normal operation of the levers 90 and 95, that is, when they moveas a unit, the movement of the fork 104 is substantially transverse tothe rod 103 so that the rod is not moved. However, when an obstructionoccurs preventing movement of the rst lever 90, the second lever 95moves relatively thereto, causing the fork 104 to move longitudinally ofthe rod and thus drawing the rod with it. Such movement of the rodswings the bell crank 106 and moves the slide 70 to a position in whichthe projection 71 engages the lugs 72 on the pawl carrier 60 and locksthe latter in a neutral position. Thus, the

feeding mechanism is rendered inoperative when any obstruction orexcessive resistance occurs which prevents depression of the saw on thecutting stroke.

vAnother safety feature of the present invention is a means for throwingout the feed mechanism at the top of the stroke of the bracket 22 incase the reversing mechanism fails to act. In the present embodiment,this means acts through the slide 70 to lock the pawl carrier 60 in aneutral position, and comprises alever 110 (see Figs. 5 and 7) mountedon a xed pivot 111 with one end extending up through an aperture 112formed in the slide 70. The other end of the lever 110 extendsdownwardly into the path of the bracket 22. On upward movement of thelatter, should the means for reversing the feed mechanism fail to actbefore the bracket strikes the end of the lever 110. the bracket willcause the lever to swing, thus moving the slide 70 to shift and lock thepawl carrier 60 in its neutral position to render the feed mechanisminoperative.

Counter-balancing device The present invention includes a new andimproved device for counter-balancing the weight of the bracket 22 andsaw frame 23 in order to render the feed mechanism more responsive tothe conditions of cutting. The embodiment shown in the drawingscomprises a means adapted to be rotated in one direction by downwardmovement of the bracket 22, and means resisting such rotation by tendingto rotate said firstmentioned means in the opposite direction. To thisend, a rod (see Figs. 3 and 4) is mounted for vertical sliding movementthrough the top of the base 20 and abuts against the underside of thebracket 22 adjacent the column 21. Within the base is a sheave 121, thegroove of which guides the lower end of the rod 120. The sheave 121 isrotatably mounted on a horizontal shaft 122 mounted within the base andheld against rotation relative thereto. To cause the sheave to rotate ondownward movement of the rod, a

chain 123 or other flexible means is secured at l one end to the lowerend of the rod and is wrapped around the sheave in the groove thereofwith its other end attached to the sheave.

The means tending to rotate the sheave in the opposite directioncomprises, in the present instance, a torsion spring 124 coiled aboutthe shaft 122 and secured thereto at one end with its other end securedto the sheave. Thus, when the sheave is rotated by the rod movingdownwardly, the spring is wound to exert a torsional force on thesheave. 'Ihe spring is made of such strength that it normally balancesthe weight of the bracket, etc., acting through the rod to turn thesheave. The sheave is held against any tendency of the spring to slideit longitudinally along the shaft as by means of a washer 125 and acotter pin 126.

The shaft 122 is held against rotation by means of a bolt 127 extendingthrough the shaft and through a boss 128 formed on the outer face of thebase 20. If it is desired to adjust the torsional force exerted by thespring, the bolt 127 may be removed and the shaft rotated in the desireddirection as by a tool inserted in a hole 129 in the outer end of theshaft.

Single cut control The present invention includes, as in the case of themachine shown in my copending application, a construction permitting themachine to lin? GTI

be set to effect a single cut through a piece of stock and then stopautomatically. To this end, I provide a dog 130 (see Figs. 1 and 2)mounted to move with the bracket 22 in a path adjacent a control rod 131which on rotation is adapted to operate a, switch 132 controlling theelectric driving motor of the machine. As shown in the drawings, the dog130 is conveniently mountedon a feed reversing dog 133 carried by thebracket. 'I'he dog 130 comprises a bell crank pivoted on a pin 134 andhaving one arm extending into the path of a finger 135 secured to thecontrol rod 131. The other arm of the bell crank is weighted and tendsto hold the first arm in said path.

On the upward travel of the bracket 22, the dog 130 is shaped so thatthe finger 135 cams the dog aside permitting it to pass. When the feedmechanism is reversed and the bracket starts down, the dog engages thelnger 135 causing it to turn the rod 131 and shut off the motor.However, the bracket is moved up and down a short distance respectivelyon the back stroke and cutting stroke by the saw relieving mechanismwhile the feeding mechanism is still moving the bracket upwardly. Itmight occur that the dog 130 just passed the finger 135 on the upwardmovement caused by the saw relieving mechanism, so that on thesucceeding depression of the saw by said relieving mechanism, the dog130 would engage the finger 135 and stop the machine while the feedingmechanism is still set for upward movement. To prevent such occurrence,before the dog turns the rod 131, it is adapted to move slightlyupwardly, as permitted by an elongated hole in which the pivot pin 134is mounted. as shown at 136, in order to have the reversal of the feedmechanism fully completed before the machine is stopped.

To render the dog inoperative when it is desired to make more than asingle cut, a stop member 137 is pivotally mounted on the feed reversingdog 133 and is adapted to be swung in a counter-clockwise direction(Fig. 2) into a position abutting a nose 138 on the dog 130 to hold thelower end of the latter out of the way of the finger 135.

It will be apparent that, when it is desired to make a single cut, thestop member 137 is swung to release the dog 130 before the bracket movesup. The dog then becomes effective on the start of the next succeedingdown stroke and stops the machine, leaving the machine in down feedingposition for the next cut.

Work feeding device As in my prior Patent No. 1,201,244, dated October17, 1916, the machine is capable of automatically feeding the workforward to a proper position for a new cut at the completion of eachcut. To this end, a work vise 140 (see Fig. 1) is slidably mounted on apair of bars 141 and is adapted to be pulled forwardly thereon by meansof a cable 142 wound on a drum rotated by a pulley 143 adapted to bedriven by a belt from the main shaft. The pulley and drum are carried ona lever 144 which normally is held in such position that the belt slipsfreely on the pulley. On upward movement of the bracket 22 after thecompletion of a cut, the lever 144 is swung to tighten the belt andcause the pulley and drum to be driven.

In my prior machine, the means for moving the lever 144 moved withbracket 22. Such a means proved to be satisfactory in smaller maa pairof levers pivoted to yLeraars chines but in larger machines where thelength of travel o f the bracket is great, space is not available topermit said means to travel such a length.

The present invention includes as a feature, means for-swingingthe-lever 144, which operates only during the upper-part of the travelof the bracket and is provided with a lost motion device permitting saidmeans to remain stationary during the other part of the travel of thebracket. To this end, a bored-out stop member 150 is secured to asuitable part of the bracket, such as the reversing dog 133 (see Fig.2), and a rod 151 slidably extends through the bore of the member 150.The lower end of the rod 151 extends through the free end of the lever144 which is yieldably supported on the rod by a collar 152 and spring153. On the upper end of the rod, a nut 154 is threaded which is adaptedto be engaged by the upper end of the stop member 150 on upward movementof the bracket so as to lift the rod with the bracket. v'I'he nut 154also constitutes a means whereby the point at which the rod is preventthe nut 154 from jarring out of adjustment, the upper part of the rod isflattened on one side, as at 155, and a spring plunger 156 is mountedwithin the nut to bear against said flattened side of the rod. The rodis also prevented from turning within the bore of the stop member 150 bya screw 157 which extends across the flattened side 155, said screw alsoserving to secure the stop member 150 to the feed re versing dog 133.

When the bracket 22 is in its top position, the rod 151 hangs from thedog 133 with the nut 154 bearing on the top of the stop member 15'0. Ondownward movement of the bracket, the rod moves therewith until itslower end strikes the base 20 and it can be lowered no farther. I'hestop member 150 then slides down along the rod. When the bracket startsits upward movement, the stop member slides up along the rod untilcoming in contact with the nut 154. Continued upward movement of thebracket carries the rod with it, and near the upper end of the travel ofthe bracket, when the saw is clear of the work, the collar 152 on thelower end of the rod acts through the spring 153 to lift the free end ofthe lever 144. The swinging of the lever 144 causes the belt drivingpulley 143 to be tightened, and the drum winds up the cable 142 to drawthe vise 140 and the work forwardly to the position for a new cut.

I claim as my invention:

1. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportdownwardly including a screw shaft, means tending to raise said shaft,means for intermittently depressing said shaft including a connectionadapted 'to yield when resistance to downward movement of said supportbecomes excessive, and means associated with said connection andactuated by the yielding thereof for rendering said feeding mechanisminoperative.

2. In a hacksaw, the combination of a reciprocable saw, a-verticallymovable support for said saw, mechanism for feeding said supportvertically including a screw shaft threaded in said support, meanstending to raise said shaft, means for intermittently depressing saidshaft including each other, said levers normally moving in unison butbeing adapted to move relatively to each other, means for renderlraisedmay be adjusted. Tol

1- tively, said means ing said feeding mechanism inoperative, and meansconnecting said last-mentioned means and one of said levers and adaptedto be actuated when said one lever moves relatively to the other.

3. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportvertically including a screw shaft threaded in said support, meanstending to raise said shaft, a first lever for depressing said shaft, asecond lever pivoted on said rst lever, means for intermittentlyactuating said second lever, means connecting said levers normallycausing them to move in unison but adapted to yield to permit said secf0nd lever alone to move, and means associated with said connection andactuated as an incident to the yielding thereof for rendering saidfeeding mechanism inoperative.

4. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportvertically including a screw shaft threaded in said support, meanstending to raise said shaft, a rst lever for depressing said shaft, asecond lever pivoted on said first lever, means for intermittentlyactuating said second lever, means normally preventing pivotal movementof said second lever on said first lever but adapted to yield to permitsuch movement, and means actuated by the pivotal movement of said secondlever on said first lever for rendering said feeding mechanisminoperative.

5. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportvertically comprising a screw shaft threaded in said support, and a pawland ratchet device for turning said screw shaft, means for moving saidpawl to an inoperative position, means tending to raise said shaft,means for depressing said shaft on the cutting stroke of said sawincluding a member adapted to yield to permit said shaft to remain inits raised position, and spring means connect-ed to said pawl-movingmeans and said member and adapted to operate said pawl-moving means whensaid member yields.

6. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportvertically including a screw shaft threaded in said support, meanstending to raise said shaft, means for depressing said shaft on thecutting stroke of the saw including a member normally movable in onepredetermined path but capable of movement in another predetermined pathwhen said shaft is prevented from being depressed, and means associatedwith said member and actuated as an incident to the movement of saidmember in said other path for throwing out the feeding mechanism.

7. In a hacksaw, the combination of a reciprocable saw, mechanism forfeeding said saw vertically, means for raising and depressing the saw onthe back stroke and the cutting stroke respecbeing yieldable to permitthe saw to remain in its raised position, and means connected with saidyieldable means and actuated as an incident to the yielding thereof forrendering said feeding mechanism inoperative.

8. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportvertically including a pair of pawl and ratchet devices for feeding saidtively, and means support up and down respecfor moving said pawls to aninoperative position, said means being actuated by said support onreaching the upper end of its stroke.

9. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportvertically including a pair of pawl and ratchet devices, one for movingsaid support up and the other for moving said support down, and acarrier for said pawls adapted to be shifted to bring the respectivepawls in operative relation to the ratchets, and means for shifting saidcarrier to a neutral position in which both pawls are inoperative, saidmeans bcing actuated by said support on reaching the upper end of itsstroke.

10. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportvertically comprising a plurality of pawl and ratchet devices, a carrierfor said pawls adapted to be shifted for moving the pawls from anoperative position to an inoperative position, means for shifting saidcarrier to a position where said pawls are simultaneously inoperative,and a lever for moving said means, said lever being actuated by saidsupport when the latter reaches the upper end of its stroke.

11. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportvertically including a pair of pawl and ratchet devices, one for movingsaid support up and the other for moving said support down, automaticmeans for moving said pawls to an inoperative position at any point inthe downward travel of said support on excessive resistance to suchtravel, and means operated by said support for moving said pawls to aninoperative position when said support reaches the upper end of itstravel.

12. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportvertically including a pair of pawl and ratchet devices, one for movingsaid support up and the other for moving said support down, means formoving said pawls simultaneously to an inoperative position, a pair oflevers for independently actuating said means, means movable in apredetermined manner on excessive resistance to the downward travel ofsaid support, and means actuated by movement of said last-mentionedmeans and operable at any point in the downward travel of said supportfor moving one of said levers, the other of said levers being movable bysaid support on reaching the upper end of its travel.

13. In a power hacksaw, the combination of a reciprocable saw, avertically movable support for said saw, means for feeding the stockforwardly for a new cut including a control lever, and means forautomatically movingsaid lever at the completion of a cut comprising arod secured to said support and having a limited sliding movementrelative thereto but adapted to move therewith during the latter part ofthe upward movement of said support, means for adjusting the movement ofsaid rod, and a resilient abutment on said rod for moving said lever.

14. In a power hacksaw, the combination of a vertically movable sawsupport, mechanism for feeding said support vertically, andcounter-balancing means for said support comprising a rod movable withsaid support, a rotatable sheave positioned to support the rod in itsgroove, a flexible member secured to the end of the rod and extendingaround said sheave to rotate the latter jusv on movement of the rod, anda torsion spring tending to rotate said sheave in a direction to raisesaid rod and said support.

15. In a power hacksaw comprising a frame and a saw support mounted forvertical movement on said frame, means for counter-balancing saidsupport comprising, in combination, a vertical rod bearing against saidsupport and guided in said frame, a sheave mounted for rotation on ahorizontal axis and guiding the lower end of said rod, a chain attachedto the lower end o1' said rod and to said sheave and extending aroundsaid sheave to rotate it on downward movement of the rod, and a torsionspring fixed at one end and secured to said sheave at the other end andtending to rotate said sheave in a direction to raise said rod.

16. In a hacksaw, a feeding mechanism comprising, in combination, ascrew shaft, a pair of ratchets for rotating said shaft respectively inopposite directions, one of said ratchets being axially movablerelatively to the other, a. third ratchet interposed between said pairof ratchets and having frictional driving contact therewith, a springcoiled aroundsaid shaft and bearing at one end against said axiallymovable ratchet, a Washer keyed to said shaft but movable longitudinally thereof and bearing against the other end of said spring, anda nut threaded on said shaft and abutting against said washer to permitadjustment of said spring, the abutting faces of said nut and washerbeing correspondingly serrated normally preventing rotation therebetween but adapted to permit relative rotation when the nut is manuallyturned.

17. In a hacksaw, the combination of a source of power, a rod having afinger mounted thereon and adapted on rotation to shut off said source,a vertically movable bracket, a dog pivotally mounted on said bracketand adapted to swing by gravity into position to strike said finger,said dog being adapted to actuate said flnger on downward movement otsaid bracket but adapted to be swung aside by said finger on upwardmovement of said bracket, and a stop member pivotally mounted on saidbracket and adapted to be' swung into engagement with said dog to holdthe latter in an inoperative position.

18. In a hacksaw, the combination oi' a source of power, means forcontrolling said source of power, a reciprocable saw blade, a verticallymovable bracket supporting said bladeffeeding mechanism for saidbracket, means for raising said vbracket on the back stroke of the bladeand for depressing said bracket on the cutting stroke, and a dog carriedby said bracket for operating said control means on downward movement ofsaid bracket, said dog having limited movement relative to said bracketto prevent operation of said control means by depression of said bracketon the cutting stroke.

19. In a power hacksaw comprising a hollow base frame having a top walland a saw support mounted for vertical movement on said frame, means forcounterbalancing said support comprising, in combination, a rod bearingagainst the underside of said support and slidably guided intermediateits ends in the top wall of said frame, a sheave rotatably mountedwithin the frame and positioned tangentially to said rod with the lowerend of the latter guided in the groove of said sheave, a flexible memberwound around said sheave with one end extending tangentially therefromand attached to the lower end of said rod, and resilient means tendingto resist rotation of said sheave in the direction caused by downwardmovement of said support.

20. In a hacksaw, the combination of a reciprocable saw, a verticallymovable support for said saw, mechanism for feeding said supportdownwardly including a member carrying said support, means tending toraise said member, means for intermittently depressing said member, saiddepressing means being yieldable on a predetermined resistance todownward movement of said support, and means connected to saiddepressing means and actuated as an incident to the yielding thereof forrendering said feeding mechanism inoperative.

GEORGE J. BLUM.

